DIGITAL EDITION

Environmental Best Practices, Part 2

(August 2008) posted on Mon Aug 27, 2007

In the first installment of this series, you learned why incorporating an environmental management system as part of a broader business plan is becoming an essential part of running any company. Here the discussion continues with a look at on-press cleaning materials and practices with a focus on identifying VOC risks.

We could be certain that the California low-VOC solvent had not evaporated to any significant extent so the weight-loss we found was simply due to solvent remaining on the mesh. The European low VOC result was identical—the amount that evaporated in this typical example of usage was effectively zero. The third, practical solvent showed a very small loss by evaporation. The acetone? Well, this was a joke. We couldn’t dip the cloth five times into the solvent because it had all disappeared after the third dip. Just the act of transferring the cloth to the screen and giving it a few wipes was sufficient for the acetone to disappear into the air.

This is an extreme example, but it graphically makes the point. Most of that acetone had simply been wasted. The environmental cost of volatile solvents is more than just the wastefulness. Even though we did the experiment in a good fume hood, the acetone smell was overwhelming. So, of course we were using a lot of energy to suck all that solvent away and throw it (along with expensive conditioned air) out to the atmosphere. Also remember, it is the vapors that can ignite and burn. Do you have any local ignition sources? How about that gas dryer or gas heater?

Let’s turn the story around the other way. The solvents that weren’t evaporating were staying on the screen doing what they were designed to do—clean the ink. Not just move the ink around. So it’s not just an environmental issue. Lower volatility solvents may cost more per pound, but they stay around much longer to do their job and can actually save you money. Many of these lower evaporative solvents are widely used in the USA, and have been for many years. Do not forget if you are using a highly volatile product, it is likely you have storage requirements you have to comply with because of the flashpoint of the product. There will be limitations on the volume you can store and how you store them.

Acetone is only regarded as a low VOC chemical in California because it has a relatively low tendency to generate harmful ozone after evaporation. But it does not have a low tendency to volatilize. Its characteristics and those of other types of press washes are compared in Table 1.